1. Field of the Invention
The invention relates to solid-state color image sensors, and more particularly to a technique for producing a plurality of color signals from a single image sensing array.
2. Discussion Relative to the Prior Art
It is a well-recognized goal to produce a plurality of color signals from a single solid-state image sensing array. Solid-state color image sensors are known wherein panchromatic image sensing elements in an array are selectively sensitized to color by means of an integral array of color filters disposed over the array of image sensing elements. Highly efficient configurations for such filter arrays that maximize the amount of usuable image information, based on human visual acuity for color detail, have been described in U.S. Pat. No. 3,971,065, issued July 20, 1976 to Bayer and U.S. Pat. No. 4,047,203, issued Sept. 6, 1977 to Dillon. The inherent resolution capabilities of such arrays are limited not only by the number of image sensing elements that can be manufactured in the array, but also by the fact that only a portion of the elements in the array contributed to the resolution of fine detail. Consequently, the spatial resolution of such integral-filter color image sensing arrays, while optimized for the particular design, will not be as high as a monochrome image sensing array of the same number of elements.
Recently, a solid-state color image sensing array has been developed having a potential resolution equal to that of a monochrome array of the same size. This array is based on a novel image sensing element having a plurality of superposed channels (e.g. three superposed channels for a three color device), each channel having a different spectral response due to the differential absorption of light by a semiconductor material. Such an array is disclosed in Research Disclosure August 1978, Vol., 172, Disclosure No. 17240 entitled "Color Responsive CCD Imager", available from Industrial Opportunities, Ltd., Homewell, Havant, Hampshire P09 1EF, UK. Although this approach represents a major breakthrough in improving the resolution of a solid-state color image sensing array, the manufacture of the multiple superposed channels for a three color array is complicated, requiring the formation of three superposed channels in the device. In addition, more information may be produced by such an array than can be efficiently utilized by a human viewer, since the spatial resolution in each of the basic colors is essentially equal. Thus, it is an object of the present invention to provide a solid-state color image sensing array that possesses the best features of both the approaches outlined above, i.e. a solid-state color image sensing array capable of producing a color signal having a spatial resolution equal to that produced by a monochrome array of comparable size, and sharing the relative simplicity and color sampling efficiency of an integral-filter color image sensing array.